Method of and apparatus for controlling carbon dioxide gaseous mixtures



Oct. 25, 1932- D. H. KILLEFFER METHOD OF AND APPARATUS FOR CONTROLLING CARBON DIOXIDE GASEOUS MIXTURES Filed Dec. 31

ITOR

ATTORNEYS Oct. 25, 1932. D. H. KILLEFFER 1,883,940

METHOD OF AND APPARATUS FOR CONTROLLING CARBON DIOXIDE GASEQUS MIXTURES Filed Dec. 31, 1930 2 Sheets-Sheet 2 jlaizm ATTORN EYS Patented Oct. .25, 1932 UNITED STATES PATENT VGFFICE DAVID E. KILLEFFER, F YONKERS, NEW YORK, ASSIGNOR TO DRYICE EQUIPMENT CORPORATION, OF NEW YORK, N. Y., A CORPORATION OI DELAWARE METHOD on AND APPARATUS non. CONTROLLING CARBON DIOXIDE eAsEoUB mrx'rnnns Application filed December 31, 1930. Serial No. 505,707.

My present invention is shown as embodied in apparatus for refrigerating by means of solid carbon dioxide, particularly apparatus of the type in which the heavy gas evaporating from the solid is discharged into the atmosphere of the refrigerated space. While certain of the products to be refrigerated are not affected by the gas and others can be easily protected from it, there are still 1a others not easily protected and which may be seriously damaged thereby. As concerns the latter class, it has been proposed to eliminate the difliculty entirely by discharging all the gas outside of the refrigerated space; also it has been proposed to allow the gas to leak out rapidly enough to avoid production of dangerous concentrations. However, experience shows that many products likely to be injured by an-atmosphere containing too great percentage of carbon dioxide gas, may be greatly benefitedby an atmosphere of air containing only certain limited percentages of the gas; for example, certain vegetables, cut flowers, fruits and the like; and one object of my invention is to regulably control the production of air-gas mixtures in proportions suitable for the atmosphere of the particular product to be preserved thereby. 7 Obviously, there are many ways in which air and gas may be mingled for such urposes, either by hand or automatic ad ust ment of inlet or outlet valves; or by leaks as above suggested, but unless very delicate apparatus is employed, the operation is complicated and rendered uncertain by variation of internal or external pressure, specific gravity of the gaseous mixture, etc. Even slight pressure variations of this kind, tend to pro- 4 duce relatively large volume flow through all ordinary leaks or vents, all gases flowing together in the same direction, either in or out, according to the direction of the pressure. Moreover, differences in weight between air and carbon dioxide gases tend to produce gravity outflow of the heavy carbon dioxide gas through low level leaks, thereby causing inflow of air through higher level leaks.

As contrasted with this non-selective, unidirectional flow, my invention contemplates employment of air inlet and gas outlet means, operating by diffusion of the gases so that different gases flow simultaneously in opposite directions, through the same passages, at rates determined by their densities, so that the flow is practically independent of the above described variations of internal or external pressures. The means which I employ for this purpose is a porous septum having one surface exposed to the air, preferably ordinary external atmosphere, and the other surface exposed to carbon dioxide gas, either pure or mixed with varying percentages of air. In such case, the air will diffuse through the pores into the carbon dioxidegas and the carbon dioxide gas will diffuse outward into the air; but other thin 5' being equal the air being lighter, will di use inward more" rapidly than the heavy carbon dioxide gas will diffuse outward. In the case of mixtures, the rate will depend upon the average densities of the bodies of gas on opposite sides of the septum. That is to say,

other things being equal, the rate of passage of air on one side of the septum into a fiftyfifty solution of gas and air on the other side of the septum, will be one-half the rate said pores would pass if the gas were pure.

The volume of transfusion of the gas will of course depend on the area, thickness and porosity of the septum.

It will be understood that the difference in functioning between a pore and an ordinary leak is the difference in their minimum diameters, that of the pore being very small as compared with that of'the leak. Consequently, a septum may be porous and yet have some passages large enough to operate as leaks, but this is undesirable. A pin hole or other passage large enough to be plainly visible will 1 and ordinary corrugated paperboard containing only the ordinary percentage of binder is amp porous for most purposes. Dry animal membranes, some kinds of parchment, leather, etc., may also be employed. Where a rigid septum is desired either for structural reasons or to withstand gas :ressures, thin, unglazed porcelain, clay or plaster of Paris slabs may be employed.

The above and other features of my invention may be more fully understood from the following description in connection with the accompanying drawings, in which Fig. 1 is a vertical sectional elevation showing more or less diagrammatically a chamber and means for properly diluting carbon dioxide gas before it. is discharged into the chamber;

Fig. 2 is a similar view of an arrangement for adjustably diluting the atmosphere of an air-gas mixture within the chamber;

Fig. 3 is an elevation corresponding to Fig. 2, viewed from the left;

Fig. 4 is a perspective View of a carton, partly broken away, showing one form of my invention applied thereto; and

Fig. 5 is a similar view showing a modified arrangement.

In Fig. 1, the chamber enclosing the atmosphere, the composition of which it is desired to control, may comprise an outer shell 1, preferably of metal with gas-tight joints. For most purposes, an inner wall or layer 2, may be provided for structural strength, usually of heat insulating material, because the diluted carbon dioxide gas mixtures are as a rule more beneficial to cut flowers and the like when the chamber is moderately refrigerated, temperatures of 40 to 50 F. be-

ing desirable in many cases. Where the container is air-tight, some form of pressure relief outlet as vent 3, may be arranged to prevent undue pressures of accumulated gas within the chamber. v

In the present case, the source of the carbon dioxide gas is shown as solid carbon dioxide 41-, enclosed in a container which may be in the form of a box 5, of balsa wood or other insulating material, enclosed in a gas-tight metal casing 6. This box may be charged with a solid through'openings which are normally closed by inner cover 7 and outer cover 8. The structure may be designated in any of the ways well known in the art for insuring heat absorption and gas evolution by the solid carbon dioxide at rates required to maintain desired temperatures within the refrigerator, and the gas may be caused to flow through ducts which may be inner and outer walls interposed as insulation to protect the cham- 9 through which the gas is conducted to andthrough an exterior porous conduit section 10 and from which it flows through pipe 11 into the atmosphere of the refrigerator.

The porous section 10 may bemerely a cylindrical tube or it may be widened to any extent required for proper dilution of the gas, and this will of course depend on the amount of gas to be diluted and its rate of flow through the porous section of the conduit. In general, the parts will be designed so that the porous area will be adequate for maximum desired dilution for the maximum amount of gas that is likely to flow through the conduit in a given time.

For lesser dilutions or lower rates of flow of the gas, I provide means for adjusting the active area of the porous section. This may be done by any form of shield that will cut off either the internal gas or the exterior air from direct contact with the surface of the porous wall. A very simple way is to provide an exterior slidable sleeve 12 which will shield the exterior surface of the conduit from the exterior air as shown. Sliding the sleeve to the left will decrease the amount of porous surface 10 that is'exposed to the air,

while sliding it in the opposite direction will increase said surface. As before stated, the circumferential dimension of the surface ex posed may be made anything desired, either by varying sizes for a cylindrical tube or varying widths for a flattened tube.

In special cases where the apparatus requires evaporation of relatively large amounts of solid carbon dioxide in order to make the desired temperature within the refrigerated space and at the same time a very dilute mixture of the carbon dioxide gas is desired in the atmosphere of the refrigerated space, part of the gas may be discharged directly into the open air instead of passing through the porous conduit 10 and pipe 11 into the refrigerated space.

So far as concerns the above method of making a desired gas-air mixture for the atmosphere of the container 1, it will be evident that any other source of carbon dioxide gas could be substituted for that shown in Fig.1. That is to say, a box like 5 could be located outside of the refrigerated space 'and could be provided with as much insulation as may be necessary to make it yield gas at a desired rate entirely independently of what may be required where it has a refrigerating function inside of the container 1 as shown in the drawings; or a tank of liquid carbon dioxide gas could be used as the source; or any other source of carbon dioxide ing from the interior.

carbon dioxide'gas. In this case, the 'porous septum is between the outer air and said atmosphere, as indicated at 10a, it being understood that the insulation 2a is fibrous like kapok or at least is too porous to prevent outflow of carbon dioxide from the atmosphere within the refrigerator and inflow of air from the exterior atmosphere. The porous septum 1011 may be a sheet of ordinary permeable pasteboard or corrugated board or unglazed porcelain or, in fact, any of the porous materials hereinbefore mentioned. IVhile the area, thickness and diflusion capacity of such a septum may be designed with reference to the rest of the apparatus, to maintain a normally adequate difiusion rate suitable for maintaining a desired CO content of the inner atmosphere, I prefer to employ a slide 13, whereby more or less of the outer surface may be cut off from access of the external air. In this case also a vent as 12a may be employed to prevent excessive internal pressures and this may be formed with a reverse bend as shown, operating as a valve on the principle of a plumbers trap. The fluid affording the seal may be a liquid or may be simply the heavy gas or air-gas mixture flow- If the interior has a normal tendency toward too high gas concentration, the intake of this vent may be extended toward the bottom of the space where the mixture is richest in carbon dioxide gas.

As shown in Fig. 3, there are two slides 13, controlling two porous septums 10a, and obviously there may be as many of them and their areas may be as great as necessary for the purpose in View.

In this connection it will be understood that while there are great difierenoes in the percentages of the carbon dioxide gas that various perishable products such as fruits and flowers will stand without injury, and

also in the percentages that are most beneficial, there are special cases where the maximum beneficial percentage is quite low. Thus, while 80% carbon dioxide may not injure rhubarb, may be all that is desirable for oranges, 20% for peaches, 15% for strawberries, etc. The point is that any desired percentage of gas-air mixture may be attained by the above or any other equivalent adjustment of the effective area of the porous septum and, in extreme cases, discharge of art of the carbon dioxide gas supply outsi e the refrigerator. Furthermore,

the ranges between helpful percentages and those that begin to be substantially injurious are so wide that in any articular apparatus it would be quite possible to get improved results by adjustment for known average con ditions in any apparatus of predetermined, tested design. For testing and standardizing, a carbon dioxide gas analysis indicator 14 may be employed as in Fig. 1; or it may be a permanent part of the equipment.

- Known or predetermined designs are shown in Figs. 4 and 5. In Fig. 4 the conftainer is a corrugated paper carton of ordinary construction, comprising the usual walls and top and bottom double flaps. The

walls are of porous permeable material, but the exterior is coated with material substantially impervious both to air and carbon dioxide gas as, for instance, bakelite varnish, except certain areas as 20, 20, which are left uncoated. The amount of such area is' determined. by the evaporation rate of the solid carbon dioxide and therequirements of the products to be preserved therein. It is of course possible to cut down the porous areas by additional varnish, to suit special cases.

Fig. 5 shows a special case of a carton where all the walls and flaps are made up with a substantially gas-tight layer, which may be alayer of asphalt or bakelite varnish and such layer may be interposed between,

the corrugated element and the outer flat layers which constitute the corrugated board. In this case, the porous difiusion element is afforded by the porous sealing tape 21. In this connection it will be understood.

that ordinary paper binder tape with only the usual thin coating of ordinary glue or paste, will be sulficiently porous to afford paths for very substantial diflusion of exterior air into the package and interior gas out of the package.

In Figs. 4 and 5, the cartons may be provided with vents of relatively-small flow capacity, suflicient to prevent substantial pressure of gas within the carton, but preferably not enough to permit inflow of air.

In both Figs. 5 and 6 the carton is broken away to show products 25 and solid carbon dioxide 26, packed therein.

It is understood that the conta ners shown in Figs. 1, 2 and 3 have the usual openings, with as-tight closures, for insertion and removai of perishable products.

I claim C 1. A method of preserving products of a class injured by over-concentrations of carbon dioxide gas, which includes enclosing said products in a refrigerating container having walls substantially impermeable to carbon dioxide gas, cooling said container and fusionmedium having external atmos here in contact with another surface thereo adjusting the effective area of the difiusion medium to control the amount of the dilution; and discharging the diluted product of said diffusion, into the atmosphere of the refrigerated space;

52. A method of preserving products of a class injured by over-concentrations of carbon dioxide gas, which includes enclosing said products in a refrigerating container,

cooling said container and producing gas v evaporating solid carbon dioxide by heat ab sorbed from within said container, diluting said gas by exposing it in cont-act with a surface of a porous diffusion medium having external atmosphere in contact with another surface thereof; and discharging the diluted product of said diffusion, into the atmos- ,phere of the refrigerated space.

4. A method of preserving products of a class injured by over-concentrations of carbon dioxide gas, which includes enclosing said products in a container; supplying carbon dioxide gas to produce an air-gas atmosphere in said container; controlling dilution of said atmosphere by diffusion through a surface of a. porous diffusion medium having external atmosphere in contact with another surface thereof. v i

'5. A method of preserving products of a class injured by over-concentrations of carbon dioxide gas, which includes enclosing said products in a container; supplying car-.

bon dioxide gas to produce an air-gas atmosphere in said container fcontrolling dilution of said atmosphere by diffusion through a surface of a porous diffusion medium having external atmosphere in contact with another surface thereof and by varying the effective diffusioncapacity of said diffusion medium.

6. Apparatus for preserving products of a class injured by over-concentrations of carbon dioxide gas, including a source of overconcentrated gas and means for diluting it, said means including a porous diffusion septuni, means for exposing the gas to be diluted in contact with a surface of said septum havcontainer, diluting said gas by ing external atmosphere in contact with another surface thereof.

7. Apparatus for preserving products of a class injured by over-concentrations of carbon dioxide gas, including a source of overconcentrated gas and means for diluting it, said means including a porous diffusion septum, means for exposing the gas to be diluted in contact with a surface of said septum having external atmosphere in contact with another surface thereof, in combination with means for adjusting the effective exposed surface of said septum.

8. A refrigerator of the type cooled by evaporation of carbon dioxide and discharge of the resulting gas into the atmosphere of the refrigerator and in combination therewith; means for diluting the gas before it is discharged into, said atmosphere, said means including a porous diffusion septum having a surface exposed to atmosphere and conduit means for passing the evaporated gas in diffusion relation to the opposite surface of said septum.

9. A refrigerator of the type cooled by evaporation of carbon dioxide a-nddischarge of the refrigerator having an inner surface exposed in diffusion relation to the refrigerated atmosphere and an outer surface exposed to the external air, a surface of said septum having a fibrous heat insulating covering that is permeable to gas and air.

11. A refrigerator having means for cooling it by evaporation of carbon dioxide and discharge of the resulting gas into the atmosphere of the refrigerator, and in combination therewith, adjustable means for diluting the gas in said atmosphere.

12. A refrigerator having means for cooling it by evaporation of carbon dioxide and discharge of the resulting gas into the atmosphere of the refrigerator, and in combination therewith, adjustable means for diluting the gas in said atmosphere, and a gas analysis indicator for determining the carbon dioxide content of the resulting mixture.

13. A refrigerator having means for cooll of the resulting gas into the atmosphere of v ing it by evaporation of carbon dioxide and discharge of the resulting gas into the atmosphere of the refrigerator, and in combination therewith, adjustable means for diluting the gas in said atmosphere, said means including a porous difiusion septum having a surface exposed to atmosphere, conduit means for passing the evaporated gas in diffusion relation to the opposite surface of said 1 5 septum, means for cutting ofii' more or less of the exposed area of the septum, and a gas analysis indicator for determining the carbon dioxide content of the resulting mixture.

Signed at New York in the county of New York, and State of New York this 30th day of December, A. D. 1930.

.' DAVID H. KILLEFFER. 

